sir

1used as a polite way of addressing a man whose name you do not know, for example in a store or restaurant, or to show respectGood morning, sir. Can I help you?Are you ready to order, sir?“Report to me tomorrow, corporal!” “Yes, sir!”“Thank you very much.” “You're welcome, sir. Have a nice day.”comparema'amsee alsomadam

2Dear Sir/Sirsused at the beginning of a formal business letter when you do not know the name of the man or people that you are dealing withDear Sir/SirsDear Sir or Madam

3Sira title that is used before the first name of a man who has received one of the highest British honors (= a knight ), or before the first name of a baronetSir Paul McCartneyThank you, Sir Paul.comparelady